With aging, elastic fiber deteriorates and is degraded, leading to the loss of elasticity of the tissues in the body. This does not simply pose problems with body stiffening or skin loosening. Pulmonary emphysema, arterial intimal sclerosis, and aortic aneurysm, which are major diseases in the elderly, and more recently, age related macular degeneration and the like, have been considered to be directly caused by elastic fiber deterioration and decomposition [Hautamaki, R. D. et al. (1997) Science 277(5334): 2002-4; Shapiro, S. D. et al. (2003) American journal of pathology 163(6): 2329-35; Stone, E. M. et al. (2004) The new England journal of medicine 351(4): 346-53; Chong, N. H. et al. (2005) American journal of pathology 166(1): 241-51]. However, the turnover of elastic fiber is very slow; if elastic fiber deteriorates and is degraded, the elastic fiber is not regenerated. Although the elucidation of the mechanisms for formation of elastic fiber is essential for research into the regeneration of elastic fiber, little is known about the molecular mechanisms for elastic fiber formation.
A major reason for the tardy progress of research into elastic fiber formation had been the lack of a good in vitro elastic fiber formation system. Conventionally, to form elastic fiber using cultured cells, not less than 10% fetal bovine serum had been required. For this reason, what in the serum is required for elastic fiber formation remained unknown. For example, it has been reported that in two-dimensional culture of a ciliary body pigment cell line that does not express elastin, elastic fiber is formed by elastin transfection [Robb, B. W. et al. (1999) Molecular biology of the cell 10(11): 3595-605]. However, that approach also uses 10% fetal bovine serum for the cultivation; the roles of factors other than elastin in elastic fiber formation remain unknown.
Use of fetal bovine serum in drugs intended to be transplanted to humans, such as cultured artificial skins and cultured artificial blood vessels, is under strict regulation; it is extremely difficult to prepare an artificial skin or artificial blood vessel containing a normal amount of elastic fiber. It has been reported that elastic fiber was formed in three-dimensional culture of smooth muscle cells or fibroblasts seeded to collagen gel or fibrin gel, and that elastic fiber formation was enhanced by using TGFβ1 and insulin in combination [Long, J. L. et al. (2003) Matrix biology 22(4): 339-50]. However, in this cultivation, because an ingredient derived from a heterologous animal, called 10% fetal bovine serum, is used in all cases, there are many problems with regard to transplantation to humans, and what is required for elastic fiber formation remains unknown. Additionally, the resulting elastic fiber is variegated and cannot be said to have a normal structure.
Therefore, to establish a cell culture technique enabling induction of elastic fiber formation even in the absence of serum is not only extremely important to the elucidation of the molecular mechanisms for elastic fiber formation, but also is in a strong demand for the development of a pharmaceutical that controls elastic fiber formation, and the development of cultured artificial skins or cultured artificial blood vessels comprising elastic fiber retaining a normal structure, and the like.